a spring has a spring constant of 400 N/m. the spring is compressed 15 cm and a 2 kg ball is placed on the spring in its compressed state. when the spring is released, what is the kinetic energy of the ball as it leaves the spring? what is the potential energy of the spring in its compressed state? what is the potential energy of the spring as the ball leaves the spring? what is the total energy of the system when the spring is compressed? as the ball leaves the spring?